JP2000165915A - Dtmf signal transmission system and communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge/recognize the DTMF signal without any error with the communication equipment (PBX) of a reception side even if the DTMF signal is transmitted through the use of communication equipment compressing a sound code. SOLUTION: Communication equipment 1 and 2 connected to PBX 4 and 5 and an ATM line 3 are provided with a DTMF signal detection part 102 detecting whether a DTMF signal is contained in sound from PBX 4 and 5, a DTMF signal monitoring part 103, a DTMF cell generation part 105 encoding and transmitting the DTMF signal, a DTMF cell decomposition part 110 decoding the encoded DTMF signal and DTMF signal generation part 115 generating the DTMF signal with the information content of the decoded DTMF signal and sending it to PBX 4 and 5. Transmission side communication equipment 1 and 2 encode the DTMF signal in a prescribed system, decode the DTMF signal encoded by reception side communication equipment 1 and 2 and reproduce the DTMF signal in the DTMF signal generation part 115 based on the content information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a push button in a communication system for compressing and transmitting a voice signal from a voice terminal device such as a telephone terminal device or a private branch exchange (hereinafter referred to as "PBX"). (Push Button:
Hereinafter, it is referred to as “PB”. ) Dual tone including signal
Multi Tone Multi Frequenc
y: Hereinafter referred to as “DTMF”. ) The present invention relates to a DTMF signal transmission method and a communication device for accurately transmitting a signal.

[0002]

2. Description of the Related Art Conventionally, in a communication system in which a voice signal is compressed by voice code using a communication device such as a multiplexing device and transmitted oppositely, a PB signal or the like transmitted from a telephone terminal device is transmitted in the same manner as a normal voice signal. The DTMF signal has also been voice code compressed and transmitted to the opposing communication device. That is, in the communication device on the transmitting side, the DTMF signal is subjected to voice code compression without special consideration and transmitted as a normal voice code compressed signal, while the received voice code compressed signal is transmitted in the receiving communication device. Is converted to a voice signal (DTMF signal) by expanding the voice code, and is transmitted to a voice terminal device such as a PBX. The voice terminal device determines / recognizes the code of the DTMF signal and performs a predetermined operation. I was

[0003]

However, when the DTMF signal is compressed and decompressed as one of the audio signals as in the above-mentioned prior art, the decompression is performed by the receiving side communication device.
There has been a problem that the TMF signal (voice signal) is out of the standard of reception and may not be recognized as a DTMF signal on the voice terminal device side such as the PBX.

In transmitting a DTMF signal, a DTMF signal is transmitted.
The communication device receiving the MF signal needs a determination time for determining the DTMF signal. During the determination time, the DTMF signal is transmitted to the opposite voice terminal device. After the DTMF sound, the DTMF signal obtained by decoding the DTMF signal is reproduced, and the DTMF sound obtained by expanding the voice code compression signal may be out of the standard for receiving the DTMF signal. There has been a problem that it may not be recognized as a DTMF signal.

[0005] An object of the present invention is to provide a communication apparatus (speech terminal device) on the receiving side which can transmit a DTMF signal without error even when a DTMF signal is transmitted using a communication apparatus which performs speech code compression.
An object of the present invention is to provide a DTMF signal transmission system and a communication device capable of determining / recognizing a signal.

[0006]

According to the present invention, in a communication device connected to a voice terminal device and a communication line, a voice signal from the voice terminal device is code-compressed to generate voice information. Voice code compression means for transmitting to a communication line, code expansion of voice-compressed voice information from the communication line to generate a voice signal, and voice signal decompression means for transmitting the voice signal to the voice terminal device; Detecting means for detecting whether or not a voice signal from a terminal device includes a DTMF signal; and, when the detecting means detects the DTMF signal, encoding the DTMF signal into a predetermined format to obtain a DTMF signal.
DTM that generates F information and sends it to the communication line
F encoding means, and encoded DT from the communication line.
DTMF decoding means for decoding MF information;
F based on the content decoded by the F decoding means.
DTMF generating means for generating an MF signal and sending the MF signal to the voice terminal device.

Further, the present invention provides a transmitting-side voice terminal device,
The transmission-side communication device that connects the transmission-side audio terminal device, the reception-side audio terminal device, and the reception-side communication device that connects the reception-side audio terminal device, and the transmission-side communication device via a communication line. In a communication system connected to the receiving communication device, the transmitting communication device generates audio information by code-compressing an audio signal from the transmitting audio terminal device, and sends the generated audio information to the communication line. Voice code compression means, and DTMF to the voice signal from the transmitting side voice terminal device.
Detecting means for detecting whether or not a signal is included; and when the detecting means detects a DTMF signal, the DTMF signal is encoded into a predetermined format to generate DTMF information and transmitted to the communication line. DTMF encoding means for generating an audio signal by code-expanding audio-compressed audio information from the communication line in the receiving-side communication device, and outputting the audio signal to the receiving-side audio terminal device. Code decompression means, DTMF decoding means for decoding coded DTMF information from the communication line, and a DTMF signal generated based on the content decoded by the DTMF decoding means, DT to be sent to the side audio terminal
MF generating means.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system configuration diagram showing the overall configuration of the present invention. In FIG. 1, this system includes one ATM multiplexer 1 and the other ATM multiplexer 2.
An ATM line 3 connecting the ATM multiplexer 1 and the ATM multiplexer 2 and a PB connected to the ATM multiplexer 1
X4 and a PBX 5 connected to the ATM multiplexer 2;
A plurality of extension telephones 44 accommodated by the PBX 4;
A plurality of extension telephones 54, an e-mail device 58 accommodated by the PBX 5, an ATM multiplexer 1 and an ATM
A public line 6 for connecting to the multiplexer 2, a centralized management terminal 7 connected to the public line 6, and an ATM multiplexer 1
And a management terminal device 9 connected to the ATM multiplexer 2.

The ATM multiplexer 1 compresses a series of voice signals from the PBX 4 into voice codes, converts them into ATM cells and transmits them to the ATM line 3, and converts the ATM cells received from the ATM line 3 into decellularized cells. After that, the voice code is expanded to return to a series of voice signals and transmitted to the PBX 5. Similarly, the ATM multiplexer 2 has a PBX
After a series of voice signals from voice signal 5 are voice code compressed, they are converted into ATM cells and transmitted to ATM line 3,
After the ATM cell received from the line 3 is decellularized, the ATM cell is decompressed into a speech code, returned to a series of speech signals, and transmitted to the PBX 4.

The PBX 4 is used to freely exchange connections between the extension telephones 44 or between the extension telephones 44 and the ATM multiplexer 1. Similarly, the PBX 5 is connected between the extension telephones 54 and the extension telephones 54. And the ATM multiplexing device 2, the extension telephone 54 and the electronic mail device 58, or the ATM multiplexing device 2 and the electronic mail device 58.

More specifically, the PBX 4 includes a communication path switch (SW) 41, an extension circuit (LIN) 43 connected to the communication path switch 41, and a communication path switch 41.
, A central control unit (CC) 45, and a main storage unit (MM) 46.

The communication path switch 41 is for freely connecting the extension circuits 43 or between the extension circuit 43 and the trunk circuit 42 to set a communication path. The extension circuit 43 controls connection of the extension telephone 44. The trunk circuit 42 has an interface function of controlling connection with the ATM multiplexer 1. Further, the central control device 45 controls the entire PBX 4 including the communication path switch 41, the extension circuit 43, and the trunk circuit 42.
Is for storing station data, tables, processing programs and the like necessary for the central controller 45 to control the entire PBX 4.

The PBX 5 has a communication path switch (SW) 51.
And the extension circuit (LI) connected to the communication path switch 51.
N) 53, a trunk circuit (TRK) 52 connected to the communication path switch 51, a mail interface circuit (I / F) 57 connected to the communication path switch 51, a central control unit (CC) 55, And a storage device (MM) 56.

The communication path switch 51 is provided between the extension circuits 43, between the extension circuit 43 and the trunk circuit 42, and between the extension circuits 54 and 54.
And the mail interface circuit 57 or the trunk circuit 52 and the mail interface circuit 57 are freely connected to establish a communication path. Extension circuit 53
Has an interface function for controlling the connection of the extension telephone 54, the trunk circuit 52 has an interface function for controlling the connection with the ATM multiplexer 2, and a mail interface circuit 57.
Has an interface function of controlling connection with the electronic mail device 58. Further, the central control unit 5
5 is a PBX including a communication path switch 51, an extension circuit 53, a trunk circuit 52, and a mail interface circuit 57.
The main storage device 56 stores station data, tables, processing programs, and the like necessary for the central control device 55 to control the PBX 5 as a whole.

With such a configuration, the ATM
The ATM communication is performed between the multiplexer 1 and the ATM multiplexer 2 via the ATM line 3. Therefore, the extension telephone 44
The PBX 4, the ATM multiplexer 1, the ATM line 3, the ATM multiplexer 2, and the PBX 5 are connected between the telephone and the extension telephone 54 or between the extension telephone 44 and the electronic mail device 58.
The communication connection (call connection) of the audio signal is enabled via.

The centralized management terminal device 7 centrally manages the ATM multiplexer 1 and the ATM multiplexer 2 at a remote place, and the ATM multiplexer 1 and the ATM multiplexer 1 are connected via the public line 6. It is connected to the multiplexing device 2 and sets various setting information necessary for the operation of the ATM multiplexing device 1 and the ATM multiplexing device 2.
The communication status (failure information) of the M multiplexing device 2 is monitored.

Further, the management terminal device 8 manages the ATM multiplexer 1, sets various kinds of setting information necessary for the operation of the ATM multiplexer 1, and sets the management information of the ATM multiplexer 1. The management terminal device 9 monitors the communication state (failure information). Similarly, the management terminal device 9 manages the ATM multiplexing device 2 and various setting information necessary for the operation of the ATM multiplexing device 2. Is set, and the communication state (failure information) of the ATM multiplexer 2 is monitored.

FIG. 2 is a diagram showing an AT according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating an internal configuration of an M multiplexing device.

In FIG. 2, ATM multiplexers 1 and A
The TM multiplexing device 2 has the same configuration. The ATM multiplexing device 1 and the ATM multiplexing device 2 communicate with each other by the trunk circuit interface units 101 and 201, the DTMF signal detection units 102 and 202, and the DTMF signal monitoring unit. Part 10
3, 203, voice code compression sections 104, 204, DT
MF cell generators 105 and 205 and voice cell generator 10
6, 206, cell multiplexing units 107, 207, ATM line interface units 108, 208, and cell separation unit 10.
9,209, DTMF cell decomposing units 110,210,
Voice cell decomposing units 111 and 211 and output information switching unit 11
2,212, DTMF signal generators 113,213,
Voice code decompression units 114 and 214 and silence generation units 115 and
215, selectors (a) 116 and 216, and selectors (b) 117 and 217.

Trunk circuit interface units 101 and 2
Reference numeral 01 denotes an interface unit for communicatively connecting the PBXs 4 and 5 (trunk circuits 42 and 52) to audio signals.
The audio signals from the PBXs 4 and 5 are converted into DTMF signal detectors 1
02, 202 and the audio code compression units 104, 204, and audio signals from the selectors (b) 117, 217 to the PBXs 4, 5.

The DTMF signal detection units 102 and 202 detect whether or not the voice signal obtained from the trunk circuit interface units 101 and 201 includes a DTMF signal.
The signals are sent to the TMF signal monitoring units 103 and 203 and the DTMF cell generation units 105 and 205. When the DTMF signal is detected, the first DTMF detection signal is continuously turned on, and the DTMF signal is output. When no signal is detected, the first DTMF detection signal is continuously turned off.

The DTMF signal monitoring units 103 and 203
DTM transmitted through TMF signal detectors 102 and 202
The F signal and the first DTMF detection signal obtained from the DTMF signal detection units 102 and 202 are received. Then, the obtained first DTMF detection signal is sampled, and from the immediately preceding signal change point (when the state changes from the ON state to the OFF state or when the state changes from the OFF state to the ON state), the next (new) A) measuring a time to a signal change point, and using the measured time as signal change detection time information;
05.

DTMF signal monitoring units 103 and 203
Always detects and analyzes the DTMF signal, and sends the detection result and the analysis result to the DTMF cell generation units 105 and 205. That is, the detected content of the DTMF signal is used as the second DTMF detection signal, and the DTMF cell generation unit 105,
When the DTMF signal is detected, the second DTMF detection signal is continuously turned on. When the DTMF signal is not detected, the second DTMF detection signal is continuously output. At the same time, and as the result of the analysis of the DTMF signal, the value information (DTMF code information) of the DTMF signal is transmitted to the DTMF cell generator 10.
5, 205.

The DTMF signal monitoring units 103 and 203
Notifies the DTMF cell generators 105 and 205 of DTMF signal status information indicating whether the DTMF signal is being detected or not at regular intervals (for example, every one second). Has a function.

The DTMF cell generation units 105 and 205
First DTM obtained from TMF signal detectors 102 and 202
An ATM cell is generated based on an F detection signal, signal change detection time information obtained from the DTMF signal monitoring units 103 and 203, a second DTMF detection signal, and DTMF signal value information (DTMF code information). A including the identification information indicating the DTMF cell and the content information of the DTMF signal
The TM cell is transmitted as information for transmitting the original DTMF signal. Note that an AT for transmitting DTMF signals is used.
The detailed configuration of the M cell (hereinafter referred to as “DTMF cell”) format will be described later.

The voice code compression units 104 and 204 compress the voice signals obtained from the trunk circuit interface units 101 and 201 according to predetermined rules and algorithms, and send them to the voice cell generation units 106 and 206. It is.

The voice cell generators 106 and 206 receive voice code compressed voice signals from the voice code compressors 104 and 204, and generate ATM cells based on the received voice signals. An ATM cell including the identification information and the content information of the voice signal compressed by the voice code is transmitted as voice information. In addition, A for audio signal transmission
The detailed configuration of the TM cell (hereinafter referred to as "voice cell") format will be described later.

The cell multiplexing units 107 and 207 include DTMF cell generation units 105 and 205 and voice cell generation units 106 and 2
Multiplex the ATM cells from 06 in the order of generation.
It is sent to the line interface units 108 and 208.

ATM line interface units 108 and 20
Reference numeral 8 denotes an ATM which is physically, electrically and logically matched with the ATM line 3 and received from the cell multiplexing units 107 and 207.
The cell is transmitted to the ATM line 3 and the AT
The ATM cell is transmitted to the M multiplexer 1 or 2, and the ATM cell is transmitted from the ATM multiplexer 1 or 2 as the opposite device.
The ATM cells received via the TM line 3 are transmitted to the cell separation units 109 and 209.

The cell separation units 109 and 209 recognize the cell type of the ATM cell received from the ATM line interface units 108 and 208 and classify the ATM cell.
If the cell is a TMF cell, the ATM cell is referred to as a DTMF cell.
The ATM cell is transmitted to the cell decomposing units 110 and 210, and when the ATM cell is a voice cell, the ATM cell is transmitted to the voice cell decomposing units 111 and 211.

The DTMF cell decomposing units 110 and 210
Upon receiving the TMF cell, it recognizes whether the DTMF cell is addressed to itself, performs ATM header processing including cell loss determination (error detection) and CPS-PH processing including channel identification and sequence number determination (error detection). After that, the DT included in the received DTMF cell is
The content information of the MF signal is recognized / analyzed to detect the signal change detection time of the DTMF signal and the value information (DTMF signal) of the DTMF signal.
Code information) to the DTMF signal generators 113 and 213, and a selector control signal for controlling the selectors (a) 116 and 216 and the selectors (b) 117 and 217 to the output information switching units 112 and 212. Things.

When voice cells are received, voice cell decomposing units 111 and 211 perform ATM header processing and CPS-PH processing in the same manner as DTMF cell decomposing units 110 and 210. This is extracted and sent to the voice code expansion units 114 and 214.

The output information switching units 112 and 212
The output of the selectors (a) 116 and 216 and the selectors (b) 117 and 217 is controlled by the selector control signals received from the F signal decomposing units 110 and 210. The contents of the audio signal output to the PBXs 4 and 5 are switched.

The DTMF signal generators 113 and 213
Signal change detection time information and DTMF value information (DTMF code information) are received from the TMF cell decomposing units 110 and 210, and a DTMF signal corresponding to the DTMF value information (DTMF code information) is generated. During the same time as the time notified as the detection time information, it is transmitted to the selectors (b) 117 and 217.

The speech code decompression units 114 and 214 decompress the speech signal received from the speech cell decomposing units 111 and 211 and compress the speech signal, and send them to the selectors (a) 116 and 216. is there.

The silence generating sections 115 and 215 always generate silence signals, and these are generated by the selectors (a) 116 and 2.
16. Note that a silent signal is a signal that allows a human to feel a silent state without any discomfort when listening to voice, and a low-level noise signal is generally used.

The selectors (a) 116 and 216 are controlled by the output information switching units 112 and 212 to output either one of the audio signals from the audio code decompression units 114 and 214 or the silent signal from the silent units 115 and 215. To the selectors (b) 177 and 217.

Then, the selectors (b) 117, 217
Are DTMF signals from the DTMF signal generators 113 and 213.
A signal or one of a voice signal and a silent signal from the selectors (b) 177 and 217 is transmitted to the trunk circuit interface units 101 and 201.

Next, the format configuration of the ATM cell used in the present invention will be described.

FIG. 3 shows an ATM adaptation layer 2
It is a figure which shows the basic structure of (AAL2) cell format. In FIG. 3, the AAL2 cell is a 5-byte ATM.
A header section F301, a 1-byte start field (STF) section F302, and an audio signal or DTM to be transferred;
A 47-byte common path sublayer protocol data unit that stores specific content information of the F signal
Payload (CPS-PDU Payload) part F3
03.

The ATM header section F301 conforms to ITU-T Recommendation I.T. 361 "Public band ISDNATM layer specification", a 4-bit GFC area, an 8-bit VPI area, a 16-bit VCI area, a 3-bit PT area, and a 1-bit CLP area ,
And an 8-bit HEC area.

The STF unit F302 includes a 6-bit OSF area for designating the storage location of the common path sublayer protocol data unit unit,
It comprises a 1-bit SN area for storing numbers and a 1-bit P area for storing parity pits. The configuration of the common path sublayer protocol data unit payload section F303 in FIG. 3 will be described with reference to FIG.

FIG. 4 shows the common path sublayer protocol data unit payload section F shown in FIG.
FIG. 3 is a diagram illustrating a format configuration of a file 303. In FIG. 4, (a) shows CPS-PDU Pa for a voice cell used when transmitting voice signals such as voice and facsimile signals.
FIG. 3 is a diagram illustrating a format configuration of a yload part;
(B) DTM including DTMF signal and SS / SR signal
CPS for DTMF cell used when transmitting F signal
It is a figure showing the format composition of a PDU Payload part.

In FIG. 4 (a), the voice cell CP
The S-PDU Payload part complies with the ITU-T Recommendation I.T. 363.2 "B-ISDN ATM adaptation layer type 2"
Common path sublayer packet header (CPS
-PH) unit F401 and a common path sublayer packet payload (CPS-PP) unit F402.

The CPS-PH unit F401 indicates the cell type, and stores the identifier "00" when the content of the voice signal to be transmitted is a normal voice signal, and stores the identifier "00" when the content of the voice signal is a facsimile signal. 2 storing the identifier "10"
Cell identification (VF) area of 6 bits and a 6-bit channel identity (CI) storing a channel identifier.
D) Store area and information indicating valid information range 6
A length indicator (LI) area of bits;
4-bit sequence number (SN) area for storing audio frame number information and 5-bit header error control (HEC) for storing error control information
The common path sublayer packet payload section F402 is configured as a voice code information storage area for storing voice code compressed voice signals. Note that this CPS-PDU for voice cells
The voice cell including the Payload portion is generated by the voice cell generation units 106 and 206 shown in FIG.

In FIG. 4B, the CPS-PDU Payload section for the DTMF cell includes a CPS-PH section F403 and a CPS-PP section F4, as in FIG. 4A.
04.

The CPS-PH unit F403 has the same configuration as the CPS-PH unit F401 in FIG.
-If the PDU Payload section is for a DTMF cell, this ATM cell is a DTMF cell in the VF area, and information on a DTMF voice signal or information on an SS / SR signal is stored in the CPS-PP section F404. The identifier "11" indicating the fact is stored. Also, CPS-
The PP unit F404 stores the SS / SR control signal in the SS
/ SR area, a signal change detection time (DTMF TIME) area for storing the signal change detection time measured by the DTMF signal monitoring units 103 and 203, and a DTMF signal presence (DV) area for storing the presence or absence of the DTMF signal. And a DTMF code (DTMF CODE) area for storing DTMF value information (DTMF code information). Note that this CPS-PDU for the DTMF cell is used.
The DTMF cell including the Payload portion is generated by the DTMF cell generation units 105 and 205 shown in FIG.

FIG. 5 shows the CPS-PP section F in the CPS-PDU Payload for the DTMF cell shown in FIG.
FIG. 4 is a diagram showing a specific configuration of a 404.

In FIG. 5, SS / SR area F501
Is a communication control signal SS / S used by the trunk circuit.
An SS / SR area for storing an R control signal. DTMF
The TIME area F502 is an area for storing the signal change detection time measured by the DTMF signal monitoring units 103 and 203 as described above, and is an area for storing time information from 0 to 126 ms. The DV area F503 is an area for storing the presence or absence of a DTMF signal as described above, and is an area where “0” is stored when there is no signal and “1” is stored when there is a signal. is there.

Also, the DTMF CODE area F504
Uses the upper 4 bits as a DTMF cell type area F504a for notifying DTMF cell type information,
The lower 4 bits are used as a DTMF code area F504b for notifying DTMF signal value information (DTMF code information). That is, the DTMF cell type area F
According to 504a, the DTMF cell transmits / stops a DTMF signal.
The notification indicates whether the cell is an off-cell, a silence cell indicating that a silence signal is to be transmitted, or a silence cancellation cell indicating that the silence signal is to be stopped. Also, the DTMF code area F504b allows the DTMF signal DTMF code “0” to
One of “9”, “*”, “#” or “A” to “D” is notified. The silent cell, the silence canceling cell, and the DTMF on / off cell will be described later in detail.

In FIG. 1, the extension telephone 44 accommodated in the PBX 4 accesses the e-mail device 58 accommodated in the PBX 5, and via the PBX 4, the ATM multiplexer 1, the ATM line 3, the ATM multiplexer 2, and the PBX 5. In some cases, the telephone connection is made, and a PB signal, which is one of the DTMF signals, is transmitted from the extension telephone 44 to control the electronic mail device 58 in some cases.

Hereinafter, taking such a case as an example, the PBX
DTM that transmits a DTMF signal from the 4 side to the PBX 5 side
The F signal transmission method will be described.

FIG. 6 is an operation sequence diagram for explaining the first embodiment according to the operation of the DTMF transmission system of the present invention.

2 and 6, a voice signal from the extension telephone 44 is transmitted through the trunk 42 of the PBX 4 to the AT.
When input to the M multiplexer 1, the ATM multiplexer 1
The audio signal is input to the audio code compression section 10 as an input audio signal via the trunk circuit interface section 101.
4 and the DTMF signal detection unit 102.

In the present embodiment, as shown in FIG. 6, the input voice signal is "voice 1", "DTM"
The following describes an example of an audio signal transmitted in the order of “F signal (audio 2)” and “audio 3”.

The voice code compression section 104 outputs “voice 1”,
Both "DTMF signal (voice 2)" and "voice 3" are voice code compressed as voice signals. Accordingly, the DTMF signal (voice 2) is also processed as one voice signal, so that the voice code compressed voice signal is transmitted from the voice code compression unit 104 to the voice cell generation unit 106 as shown in FIG. Here, it is assumed that the voice code compression unit 104 requires a processing time Va for voice code compression processing.

The voice cell generation unit 106 successively uses the received voice code-compressed voice signal as shown in FIG.
CPS-PDU Payloa for voice cell shown in (a)
In addition to generating d, an ATM header and an STF are added thereto to generate a voice cell, which is transmitted to the cell multiplexing unit 107.

On the other hand, the DTMF signal detecting section 102 receives a voice signal (input voice signal) and constantly monitors the content of the signal. The DTMF signal is determined at a determination time Dt required for the DTMF determination.
When a signal (voice 2) is received, the first DTMF detection signal is turned on and output.

Upon recognizing the ON state of the first DTMF detection signal output from the DTMF signal detection unit 102, the DTMF cell generation unit 105 generates a DTMF cell CPS-PDU Payload shown in FIG. DT of the DTMF CODE area F504 shown in FIG.
The code of the silent cell is stored in the MF cell type area F504a, and an ATM header and an STF are added thereto to generate a DTMF cell (hereinafter, referred to as a "silent cell").

Also, the DTMF signal monitoring unit 103
The first DTMF detection signal from the MF signal detection unit 102 is sampled at, for example, 1 ms to detect a change point in the on / off state of the first DTMF detection signal, and when the change is detected (from on to off) When it changes, or
When the state changes from off to on), the DTMF cell generator 1
At 05, a request is made to transmit a DTMF cell. In addition, DTM
The DTMF guard function is set in the F signal monitoring unit 103, and if the ON state does not continue for the preset guard time Gt or more, the first DTMF detection signal changes from the OFF state to the ON state. Processing not considered to be performed.

Accordingly, the DTMF signal detection unit 102
When the DTMF signal (voice 2) is detected and the first DTMF detection signal is continuously turned on for the guard time Gt or more, the DTMF signal monitoring unit 103 outputs the second DTMF detection signal as shown in FIG. Output as ON state. At the same time, the DTMF signal monitoring unit 103 outputs the first DTMF signal from the DTMF signal detection unit 102 from the time when the DTMF signal is detected (the time when the second DTMF detection signal is turned on).
The DTMF cell generation unit 105 is notified of the signal change detection time obtained by adding the guard time Gt to the time from when the F detection signal changes from the on state to the off state, and the DTMF signal value information (DTMF code information). .

The guard time Gt is set (stored) in a flash ROM provided in the DTMF signal monitoring unit 103, and is appropriately set by the management terminal device 8 or the central management terminal device 7. Can be set, and a detailed description of this setting will be described later.

The DTMF cell generation unit 105 recognizes that the second DTMF detection signal from the DTMF signal monitoring unit 103 has changed to the ON state, and also receives the signal change detection time and the DTMF signal from the DTMF signal monitoring unit 103. When the value information (DTMF code information) is received, the CPS-PDU Payload for DTMF cell shown in FIG. 4B is created, and the DTMF TIME area F5 shown in FIG.
02 indicates the signal change detection time, “1” indicating that the DTMF signal is present in the DV area, and DTMF CODE area F
A code indicating a DTMF on / off cell is set in a DTMF cell type area F504a of 504, and a DTMF indicating a value of a received DTMF signal is set in a DTMF code area F504b.
A DTMF cell (hereinafter referred to as "DTMF on cell") is stored by storing a code, and an ATM header and STF are added thereto.
Is generated and transmitted to the cell multiplexing unit 107.

Further, the DTMF signal detecting section 102 outputs
When the non-detection of the MF signal is recognized, the first DTMF detection signal is changed from the on state to the off state, and when the DTMF cell generation unit 105 detects that the first DTMF detection signal is changed to the off state, FIG. In addition to creating a CPS-PDU Payload for DTMF cell shown in FIG.
DTMF of the DTMF CODE area F504 shown in FIG.
The code of the silence canceling cell is stored in the cell type area F504a, and an ATM header and an STF are added thereto to generate a DTMF cell (hereinafter, referred to as a "silence canceling cell") and send it to the cell multiplexing unit 107. .

Furthermore, the DTMF signal monitoring unit 103
When the non-detection of the MF signal is recognized, the second DTMF detection signal is changed from the on state to the off state, and the DTMF cell generation unit 105 detects that the second DTMF detection signal is changed to the off state. In addition to creating a CPS-PDU Payload for DTMF cell shown in FIG.
In the DV area shown in FIG. 5, "0" meaning that there is no DTMF signal, and the DT of the DTMFCODE area F504
A code indicating a DTMF on / off cell is stored in the MF cell type area F504a, and an ATM header and an STF are added thereto to generate a DTMF cell (hereinafter, referred to as a "DTMF off cell"), which is transmitted to the cell multiplexing unit 107. I do.

In the cell multiplexing section 107, the ATM generated by the DTMF cell generating section 105 and the voice cell generating section 106
The cells (DTMF cells or voice cells) are transmitted to the opposing ATM multiplexer 2 via the ATM line interface unit 108 and the ATM line 3 in the order of the cell transmission request. Note that the DTMF cell generation unit 105 and the voice cell generation unit 10
If the cell transmission request is issued simultaneously from the DTMF6, the DTMF
The DTMF cell from the cell generation unit 105 is processed with priority. Therefore, from the ATM multiplexer 1, the signal shown in FIG.
, A voice cell is continuously transmitted. During the transmission, a silent cell is obtained at time (b), a DTMF on cell is obtained at time (c), a silence release cell is obtained at time (2), and a DTM is obtained at time (e).
An F off cell will be transmitted.

Next, the operation of the ATM multiplexer 2 on the ATM cell receiving side will be described.

An ATM cell (voice cell or D cell) is transmitted to the ATM multiplexer 2 after a transmission delay time D due to a trunk line or the like.
(TMF cell).

Upon receiving the ATM cell via the ATM line interface unit 208, the cell separation unit 209
CPS-PH part F of ATM cell shown in (a) or (b)
Read information stored in the VF area in 401,
It is determined whether the received ATM cell is a voice cell or a DTMF cell, and if the received ATM cell is a voice cell, the received ATM cell is determined.
The cell is transmitted to the voice cell decomposing unit 211. If the cell is a DTMF cell, the received ATM cell is transmitted to the DTMF cell decomposing unit 210.

When receiving a voice cell (received voice cell), voice cell decomposing section 211 performs ATM header processing, CP
An S-PH process or the like is performed to extract an audio signal that has been subjected to audio code compression, and sends it to the audio code expansion unit 214.

When the voice code expansion section 214 receives a voice signal that has undergone voice code compression, it decodes / expands it and outputs it as a voice code expansion section output to the selector (a) 21.
Send to 6. Here, decoding / decompression requires a decoding processing time Vb.

On the other hand, the DTMF cell decomposing unit 210
When the DTMF cell transmitted at the time point (b) is received and it is recognized that the cell is a silent cell, the output information switching unit 212 is instructed to switch the selector (a) 216. That is, the output information switching unit 212 recognizes that the silent cell has arrived, and switches the selector (a) 216 so that the output of the selector (a) 216 becomes a silent signal transmitted from the silent generating unit 215.

Next, the DTMF cell disassembly unit 210
When the DTMF cell transmitted at time (c) in is received and it is recognized that this is a DTMF on-cell,
The output information switching unit 212 is instructed to switch the selector (b) 217. That is, the output information switching unit 212
Recognizing that the TMF on-cell has arrived, the selector (b) 2 outputs the selector (b) 217 so that the output of the selector (b) 217 becomes the DTMF signal transmitted from the DTMF signal generator 213.
Switch 17

At the same time, the DTMF cell disassembly unit 210 notifies the DTMF signal generation unit 213 of the signal change detection time and the DTMF signal value information (DTMF code information) included in the received DTMF on-cell, and Generates a DTMF code corresponding to the information content,
It is instructed to send it as the signal generator output. Accordingly, at this time, the selector (b) 217 outputs the signal change detection time and DT included in the received DTMF on-cell.
DT corresponding to MF signal value information (DTMF code information)
The MF signal is reproduced and output.

Next, the DTMF cell disassembly unit 210
When the DTMF cell transmitted at the time point (2) is received and it is recognized that the DTMF cell is a silent release cell, the output information switching unit 212 is instructed to switch the selector (a) 216. That is, the output information switching unit 212 recognizes that the silence canceling cell has arrived, and selects the selector (a) 216
The selector (a) 217 is switched so that the output of the selector (a) becomes an audio signal transmitted from the audio code expansion unit 214.

When the DTMF cell disassembly unit 210 receives the DTMF cell transmitted at the time point (e) in FIG. 6 and recognizes that it is a DTMF off cell,
The output information switching unit 212 is instructed to switch the selector (a) 216 and the selector (b) 217. That is, the output information switching unit 212 recognizes that the DTMF off cell has arrived, and outputs the output of the selector (a) 216 to the silence generation unit 2.
No. 15 is generated, and the output of the selector (b) 217 is output from the selector (a) 216 so that the selector (b) 217 outputs a silent signal. . And the output information switching unit 2
A timer 12 counts that a silence signal has been transmitted from the selector (b) 217 for a certain period of time Et, and then switches the selector (a) 216 to select the selector (b) 21.
7 so as to be an output from the selector (a) 216 (an audio signal output from the audio code decompression unit 214).
The selector (b) 217 is switched.

The predetermined time Et is for preventing an echo due to a wraparound of the DTMF signal transmitted by the DTMF signal generator 213.

By the above operation, the selector (b) 217
Is an output audio signal shown in FIG. 6, and this output audio signal is
To the PBX via Therefore, the DTMF signal can be transmitted accurately without the voice compressed / expanded DTMF signal being input to a voice terminal device such as a PBX.

Next, a configuration and a method for setting the guard time Gt in the DTMF signal monitoring unit 103 will be described.

FIG. 8 is a diagram showing the configuration of a system and the configuration of an ATM multiplexer which enable the guard time Gt to be set arbitrarily.

In FIG. 8, the ATM multiplexer 1 includes:
As described above, the DTMF signal monitoring unit 103 is provided, and the DTMF signal monitoring unit 103 includes a flash ROM (F-ROM) 10 for storing the guard time Gt.
3a is provided. In addition, the ATM multiplexer 1 includes an ATM multiplexer management unit 118, a management terminal interface 119 that interfaces with the management terminal 8, and a public interface that interfaces with the public line 6 such as ISDN. A line interface unit 120 is provided.

The ATM multiplexer management section 118 has a DTM
It has a function of writing (or rewriting) the contents (data) to the flash ROM 103a in the F signal monitoring unit 103, and this is a function of the management terminal device 8 connected to the management terminal interface unit 119 or the public terminal. It operates according to a setting operation from the centralized management terminal device 7 connected via the line interface unit 120 and the public line 6. That is, by manually operating the central management terminal device 7 or the management terminal device 8, the flash ROM 1
At 03a, a guard time Gt most suitable for the configuration of the entire system can be set (stored).

The ATM multiplexing device 2 also has an AT
Similarly to the M multiplexer 1, the DTMF signal monitoring unit 203 has a flash ROM (F
-ROM) 203a, an ATM multiplexing device management unit 218, a management terminal interface unit 219 for interfacing with the management terminal device 9, and an IS
The provision of the public line interface unit 220 for interfacing with the public line 6 such as a DN makes it possible to set (store) the guard time Gt most suitable for the configuration of the entire system in the flash ROM 203a.

In the present embodiment, the guard time Gt
30 ms (millisecond), 40 ms, 50 ms, 6
0ms, 80ms, 100ms, 120ms, 150m
The configuration is such that any one of s, 180 ms, 200 ms, and 250 ms can be selectively set.
As described above, by setting the guard time Gt as appropriate, it is possible to adapt to various communication standards. In the case of a communication standard in which the transmission and reception time of the DTMF signal is specified to be 45 ms or more, the processing is required. If the guard time Gt is set to 40 ms in consideration of the delay time, it is possible to conform to the communication standard.

Further, if the DTMF signal transmission time of the connected voice terminal is guaranteed to be, for example, 100 ms or more, the guard time Gt can be set to a large value such as 100 ms. Even if the input (for example, the input of a real voice) includes a frequency component of the DTMF signal or a frequency component similar to the frequency component of the DTMF signal, this is erroneously detected as a DTMF signal. Is extremely small, and the reliability of the operation can be improved.

Further, since the guard time Gt can be set by the central control device 7 installed at a remote place, the value can be easily changed even after the system enters the operation state, and the voice input can be performed. Nevertheless, even if the erroneous detection of a DTMF signal occurs, the central control device 7 can be used to quickly change the value of the guard time Gt from a remote location to a larger value, thereby erroneously inputting the DTMF signal. Since the signal can be prevented from being detected, the serviceability is improved.

The guard time Gt can be switched between a value used at the time of call connection (basic value) and a value used during a call. Therefore, at the time of call connection, in order to quickly perform the call connection process, in a communication standard in which the transmission and reception time specification of the DTMF signal is specified as 45 ms or more, the transmission time of the DTMF signal is specified as 45 ms or more. The guard time Gt is set to 40 ms so that the minimum time conforms to the communication standard. During a call, the value of the guard time Gt is set to prevent a voice signal from being erroneously detected as a DTMF signal. 1
00 ms.

Further, in the DTMF signal monitoring unit 103, when the guard time Gt is not set in the flash ROM 103a or in the case of a call connection, the transmission and reception time of the DTMF signal is the minimum value (for example, 40) that conforms to the communication standard.
ms) can be fixedly used as the guard time Gt. In this way, the system setting from the central management terminal device 7 or the management terminal device 8 can be performed efficiently.

Next, the operation of the second embodiment when the DTMF guard function is not set in the DTMF signal monitoring unit 103 of the ATM multiplexer 1 will be described.

FIG. 7 is an operation sequence diagram for explaining a second embodiment of the operation of the DTMF transmission system according to the present invention.

Hereinafter, in FIGS. 2 and 7, the voice code compression section 104 performs voice code compression on all of "voice 1", "DTMF signal (voice 2)" and "voice 3" as voice signals. As shown in FIG. 7, the audio signal that has been subjected to the audio code compression is transmitted from the audio code compression unit 104 to the audio cell generation unit 10.
6 is sent. Here, it is assumed that the voice code compression unit 104 requires a processing time Va for voice code compression processing.

The DTMF signal detection unit 102 receives an audio signal (input audio signal) and constantly monitors the content of the signal. Then, the determination time D required for the DTMF determination
The DTMF signal is determined at t, and when the DTMF signal (voice 2) is received, the first DTMF detection signal is turned on.

On the other hand, the DTMF cell generation unit 105
When the MF signal detection unit 102 recognizes that the first DTMF detection signal has changed to the ON state, a silent cell is generated,
This is transmitted to cell multiplexing section 107.

When the DTMF signal detector 102 detects a DTMF signal (voice 2) as shown in FIG.
Since the TMF signal monitoring unit 103 also detects the DTMF signal (voice 2) almost simultaneously, it changes the second DTMF detection signal from the ON state to the OFF state, and also detects the signal change detection time and the DTMF value information (DTMF code). Information) to the DTMF cell generation unit 105.

The DTMF cell generation unit 105 recognizes that the second DTMF detection signal from the DTMF signal monitoring unit 103 has changed to the ON state, and also receives the signal change detection time and the DTMF signal from the DTMF signal monitoring unit 103. When the value information (DTMF code information) is received, the DT shown in FIG.
In the MF TIME area F502, the signal change detection time is set, and in the DV area, "1" indicating the presence of the DTMF signal is set.
A code indicating a DTMF on / off cell is set in a DTMF cell type area F504a of a DTMF CODE area F504.
Further, the DTMF code area F504b
A DTMF on-cell storing a DTMF code indicating the value of the F signal is generated and transmitted to the cell multiplexing unit 107.

Further, the DTMF signal detection unit 102
Recognizing that the MF signal has not been detected, changing the first DTMF detection signal from the ON state to the OFF state, and generating a silence canceling cell when the DTMF cell generation unit 105 detects the OFF state of the first DTMF detection signal. And the cell multiplexing unit 10
7

Further, the DTMF signal monitoring unit 103 outputs
Recognizing that the MF signal has not been detected, changing the second DTMF detection signal from the ON state to the OFF state, and when the DTMF cell generation unit 105 detects the OFF state of the second DTMF detection signal, it generates a DTMF off cell. Is transmitted to the cell multiplexing unit 107.

In the cell multiplexing section 107, D
ATM cells (DTMF cells or voice cells) generated by the TMF cell generation unit 105 and the voice cell generation unit 106 are arranged in the order of the cell transmission request in the ATM multiplexing apparatus 2 which is opposed via the ATM line interface unit 108 and the ATM line 3. To be transmitted. When a cell transmission request is simultaneously generated from the DTMF cell generation unit 105 and the voice cell generation unit 106, the DTMF cell from the DTMF cell generation unit 105 is processed with priority. Therefore, from the ATM multiplexer 1,
A voice cell is continuously transmitted from (f) in FIG. 7, and a silence cell and a DTMF on cell are transmitted at a time (g) during the transmission, and a mute release cell and DT are transmitted at a time (h).
An MF off cell will be sent.

Next, the operation of the ATM multiplexer 2 on the ATM cell receiving side will be described.

The ATM multiplexer (2) receives an ATM cell (voice cell or D) through a transmission delay time D due to a trunk line or the like.
(TMF cell).

Upon receiving the ATM cell via the ATM line interface unit 208, the cell separation unit 209 determines whether the received ATM cell is a voice cell or a DTMF cell. The ATM cell is transmitted to the voice cell decomposing unit 211, and if the cell is a DTMF cell, the received ATM cell is transmitted to the DTMF cell decomposing unit 210.

Upon receiving a voice cell (received voice cell), voice cell decomposing section 211 performs ATM header processing, CP
An S-PH process or the like is performed to extract an audio signal that has been subjected to audio code compression, and sends it to the audio code expansion unit 214.

When the audio code expansion section 214 receives an audio signal that has been subjected to audio code compression, it decodes the audio signal and outputs it as an audio code expansion section output.
Send to Here, decoding requires a decoding processing time Vb.

On the other hand, the DTMF cell decomposing unit 210
Recognizing the silent cell transmitted and the DTMF on cell transmitted at the point (g) in the above, the output information switching unit 212 is instructed to switch the selector (a) 216 and the selector (b) 217, and the output from the selector (a) 216 is output. Is made to be a silence signal sent from the silence generating section 215, and the output from the selector (b) 217 is made to be a DTMF signal sent from the DTMF signal generating section 213.

At the same time, the DTMF cell decomposing unit 210 receives the DTMF signal received by the DTMF signal generator 213.
The signal change detection time and the DTMF signal value information (DTMF code information) included in the F-on cell are notified to the DTMF signal generation unit 213, and the DTMF signal corresponding to the information contents is notified.
An instruction is issued to generate an F code and transmit it as a DTMF signal generator output. Therefore, at this time, the selector (b) 217 outputs the signal change detection time and the DTMF signal value information (DT) contained in the received DTMF on-cell.
A DTMF signal corresponding to the MF code information is output.

Next, the DTMF cell disassembly unit 210
And DTM released at time (h)
When recognizing the F off cell, the output information switching unit 212 is instructed to switch the selector (b) 217, so that the output of the selector (b) 217 becomes the output from the selector (a) 216. 217 so that a silence signal is transmitted.

The output information switching section 212 is provided with a DTMF
A timer counts the elapse of a predetermined time Et from the recognition of the off-cell reception, and thereafter, the selector (a) 21
6 so that the output of the selector (b) 217 becomes the output from the selector (a) 216 (the audio signal output from the audio code decompression unit 214).
Switch.

By the above operation, the selector (b) 217
Is an output audio signal shown in FIG. 7, and this output audio signal is
To the PBX via Therefore, the DTMF signal that has been compressed / decompressed is not input to a voice terminal device such as a PBX, and the DTMF signal can be transmitted accurately in a short time.

Thus, the extension 4 of the PBX 4
4, the DTMF signal as well as the voice signal can be accurately transmitted to the voice mail device 58.

As described above, the DTMF signal monitoring units 103 and 203 determine whether the DTMF signal is detected or not detected at predetermined intervals (for example, one second). DTMF signal status information indicating
It has a function of notifying the TMF cell generation units 105 and 205. Then, the DTMF cell generation units 105 and 205
DTMF On-Cell or DTMF
An F-off cell is being transmitted.

This function is performed by the ATM multiplexer which receives the DTMF on cell according to the embodiment of the present invention.
This is necessary because the DTMF off-cell is received after the TMF signal is transmitted, and the DTMF signal is stopped. That is, due to the failure or malfunction of the ATM line, the DTMF off-cell is lost on the ATM line,
This prevents a state in which the M multiplexing apparatus cannot receive the DTMF off cell and continues to transmit the DTMF signal.

[0113]

As described above, according to the present invention, in a communication system using voice code compression, a DTMF signal is encoded and transmitted, and a DTMF signal transmitted as voice is silence-processed to convert the DTMF signal. Reproduction can be performed within the specified value, and DTMF signal transmission can be performed without error.

Therefore, even if a voice terminal such as a PBX is connected using a communication device having a voice code compression function such as an ATM multiplexing device, in addition to the operation of the voice mail device by the DTMF signal, the transfer, voice, etc. It is possible to use additional communication service functions such as a guidance function.

Further, by adding a DTMF guard function to the DTMF signal monitoring unit, there is an effect of reducing the frequency of erroneously detecting voice input as a DTMF signal.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an overall configuration of the present invention.

FIG. 2 is a block diagram showing an internal configuration of the ATM multiplexer according to the embodiment of the present invention.

FIG. 3 is a diagram showing a basic configuration of an ATM cell AAL2 format.

FIG. 4 is a diagram showing a configuration of a common path sublayer protocol data unit payload section shown in FIG. 3;

FIG. 5 is a diagram showing a specific configuration of a common path sublayer packet payload for a DTMF cell.

FIG. 6 shows a first example of the operation of the DTMF transmission system according to the present invention.
FIG. 13 is an operation sequence diagram for explaining the embodiment.

FIG. 7 shows a second example of the operation of the DTMF transmission system according to the present invention.
FIG. 13 is an operation sequence diagram for explaining the embodiment.

FIG. 8 is a diagram showing a system configuration and a configuration of an ATM multiplexing device that can arbitrarily set a guard time of a DTMF signal monitoring unit.

[Explanation of symbols]

 1,2: ATM multiplexing device 3: ATM line 4,5: PBX 6: Public line 7: Centralized management terminal device 8,9: Management terminal device 101,201: Trunk circuit interface unit 102,202: DTMF signal detection unit 103, 203: DTMF signal monitoring unit 104, 204: voice code compression unit 105, 205: DTMF cell generation unit 106, 206: voice cell generation unit 107, 207: cell multiplexing unit 108, 208: ATM line interface unit 109, 209 : Cell separation units 110, 210: DTMF cell decomposition units 111, 211: Voice cell decomposition units 112, 212: Output information switching units 113, 213: DTMF generation units 114, 214: Voice code decompression units 115, 215: Silence generation units 116, 216: selector (a) 117, 217: selector (b)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Ohashi 94, Kojiyama City, Fukushima Prefecture

Claims (9)

[Claims] 1. A communication device connected to a voice terminal device and a communication line, wherein the voice signal from the voice terminal device is code-compressed to generate voice information, and the voice code is transmitted to the communication line. Means for generating a voice signal by sign-expanding voice-compressed voice information from the communication line;
Voice code decompression means for transmitting the signal to the voice terminal device, detection means for detecting whether a DTMF signal is included in the voice signal from the voice terminal device, and when the detection means detects the DTMF signal, DTMF encoding means for encoding the DTMF signal into a predetermined format to generate DTMF information and sending the DTMF information to the communication line, and DT for decoding coded DTMF information from the communication line.
A communication apparatus comprising: an MF decoding unit; and a DTMF generation unit that generates a DTMF signal based on the content decoded by the DTMF decoding unit and sends the DTMF signal to the voice terminal device. 2. A communication system comprising: means for converting voice information and DTMF information into ATM cells and sending them to the communication line; and means for converting ATM cells from the communication line into voice information and DTMF information. 2. The method according to claim 1, wherein
The communication device as described. 3. The communication apparatus according to claim 1, wherein said detecting means detects the DTMF signal as a DTMF signal when the DTMF signal continues for a preset time. 4. The communication device according to claim 3, further comprising setting means for variably setting a time until the DTMF signal is detected. 5. A transmission-side voice terminal device, a transmission-side communication device for connecting the transmission-side voice terminal device, a reception-side voice terminal device, and a reception-side communication device for connecting the reception-side voice terminal device. A communication system in which the transmitting-side communication device and the receiving-side communication device are connected via a communication line, wherein the transmission-side communication device performs code compression on a voice signal from the transmission-side voice terminal device to generate voice information. And a voice code compressing means for transmitting the same to the communication line; a detecting means for detecting whether a voice signal from the transmitting side voice terminal device includes a DTMF signal;
DTMF encoding means for encoding the DTMF signal into a predetermined format when detecting the F signal to generate DTMF information and transmitting the DTMF information to the communication line; Voice code expansion means for generating a voice signal by code-decompressing voice-compressed voice information from a line, and transmitting the signal to the receiving-side voice terminal device; and decoding coded DTMF information from the communication line DTMF decoding means for generating a DTMF signal based on the content decoded by the DTMF decoding means, and transmitting the DTMF signal to the receiving-side voice terminal device
A DTMF signal transmission system, comprising: an F generator. 6. The transmitting-side communication device further includes means for converting voice information and DTMF information into ATM cells and transmitting the ATM cells to the communication line. The receiving-side communication device further includes: 4. The DTMF signal transmission system according to claim 3, further comprising means for converting ATM cells from the line into voice information and DTMF information. 7. The DTMF signal transmission system according to claim 5, wherein said detecting means detects the DTMF signal as a DTMF signal when the DTMF signal continues for a preset time. 8. The DTMF signal transmission system according to claim 7, wherein said transmitting side communication device further comprises a setting means for variably setting a time until said detecting means detects said DTMF signal. . 9. The DTMF signal transmission system according to claim 5, wherein said transmitting voice terminal device and said receiving voice terminal device are both private branch exchanges.